The present invention relates to a position detecting apparatus for a trolley camera on a trolley for a container crane, for example, and can be applied to all machines for carrying a cargo lifted by a wire rope, such as a transfer crane, overhead crane, and the like.
Conventionally, a container crane etc. are used when cargoes piled on the ground are loaded on a ship alongside a pier or cargoes on a ship are unloaded and piled on the ground. In such cargo handling work, the cargo is controlled so that the swing of cargo is decreased, and the lifted cargo is landed accurately at a target position by using a landing control device, described later.
With the conventional landing control device, a cargo is hung with a lifting wire via a hoisting accessory, the crane is run to the target position along the rails in this state, the trolley is moved to the target position along the girder, the swing amount of lifted cargo is subsequently detected by a sensor (the swing amount is detected as an inclination angle with respect to the vertical line by photographing a target on the hoisting accessory with a camera installed on the trolley), and the movement of the trolley is controlled based on this detection value, by which the swing of lifted cargo is made as small as possible, and the lifted cargo is landed at the time when the swing amount becomes within an allowable value.
For the above-mentioned landing control device for hoisting accessory, the trolley on the girder is first stopped correctly at a predetermined position, the swing amount of the hoisting accessory is then detected by a swing sensor, and swing stopping control is carried out based on this detection value, by which the cargo is landed at the target position. The position of the trolley camera on the trolley at this time is successively detected by detecting the travel amount from the reference point provided on the girder by using an encoder (not shown).
However, if the deflection of the support leg or girder is changed, or a shift occurs between the crane wheel and the rail because of the movement of trolley on the girder or the change of the weight of lifted cargo, a shift of reference point on the girder is produced by the resultant horizontal travel amount, which produces a measurement error, so that the detection accuracy of the trolley position or trolley camera position is worsened. As a result, the landing accuracy is also decreased.
The present invention was made in view of such a situation, and accordingly an object thereof is to provide a trolley camera position detecting apparatus in which the position of a hoisting accessory is detected accurately, whereby the accuracy of landing position control can be increased.
To solve the problem with the above-described prior art, the present invention provides a trolley camera position detecting apparatus configured so that a trolley camera is installed on a trolley travelling on a girder, a leg target which runs together with a crane is provided at a position a predetermined distance apart from the center of a rail on which the crane runs, a girder camera is installed on the girder at a position a predetermined distance apart in the same way, an inclination angle xcex8cg between the camera centerline and the leg target is measured by the girder camera, a clinometer is installed to the girder camera to measure an inclination angle xcex8kg of the clinometer with respect to the vertical line, a horizontal travel amount xcex4g of a reference point on the girder with respect to the rail center is measured by a measuring instrument, a constant value xcex4o relating to the horizontal travel amount is calculated as
xcex4o=xcex4goxe2x88x92Hg(xcex8cgoxe2x88x92xcex8kgo)
(where, Hg is a height from the leg target to the girder camera)
in advance by using the initial values xcex8cgo, xcex8kgo, and xcex4go of the measured values, and on the other hand, the inclination angles xcex8cg and xcex8kg are measured every moment during cargo handling operation, a changing horizontal travel amount xcex4g from the reference point on the girder is calculated as
xcex4g=xcex4o+Hg(xcex8cgxe2x88x92xcex8kg)
by using these measured values xcex8cg and xcex8kg and the constant value xcex4o, and the position of the trolley camera with the rail center being a reference is corrected by using the horizontal travel amount xcex4g.
With the trolley camera position detecting apparatus in accordance with the present invention, the inclination angle xcex8cg between the camera centerline and the leg target at the lower part of a leg is measured by the girder camera, the inclination angle xcex8kg of the clinometer with respect to the vertical line is measured by the clinometer on the girder, the horizontal travel amount xcex4g due to the inclination of crane leg on the rails is measured by a transit (measuring instrument) etc., the constant value relating to the horizontal travel amount xcex4o=xcex4goxe2x88x92Hg(xcex8cgoxe2x88x92xcex8kgo) is calculated by using the initial values, the inclination angles xcex8cg and xcex8kg are measured every moment during cargo handling operation (during control), the horizontal travel amount of the reference point on the girder xcex4g=xcex4o+Hg(xcex8cgxcex8kg) is calculated by using these measured values xcex8cg and xcex8kg and the constant value xcex4o, and the position (distance) xcex4 is corrected by using xcex4g thus calculated.
As described above, the trolley camera position detecting apparatus in accordance with the present invention is configured so that the girder camera is installed to the girder, the clinometer is installed to the girder camera, the constant value relating to the horizontal travel amount of girder reference point is calculated in advance by using the output values thereof, and on the other hand, the horizontal travel amount is calculated by using the output values of the girder camera and clinometer measured every moment and the constant value, and the position of the trolley camera with the rail center being the reference is corrected by using this horizontal travel amount. Therefore, the position of hoisting accessory can be detected accurately, whereby the accuracy of landing position control of hoisting accessory can be increased.